Final answer:
After glycolysis, the six-carbon molecule of glucose is split into two three-carbon molecules of pyruvate. Pyruvate is the only molecule that can be used after this splitting during glycolysis, leading to the production of ATP and NADH.
Step-by-step explanation:
The molecule that can be used after the six carbon molecule is split during glycolysis is pyruvate. Glycolysis begins with a single glucose molecule, which is a six-carbon structure. Through a series of enzymatic reactions, glucose is first phosphorylated and converted to fructose-1,6-bisphosphate. This molecule is then split into two three-carbon molecules of glyceraldehyde-3-phosphate. Eventually, these molecules undergo further reactions where each is converted into pyruvate, resulting in the production of ATP and NADH.
The breakdown of glucose during glycolysis involves an investment of 2 ATP molecules and results in a net gain of 2 ATP and 2 NADH molecules for each glucose molecule. The critical end product of glycolysis is two molecules of pyruvate. Thus, the correct answer to the question is 2) Pyruvate.